objtool: Support GCC 8's cold subfunctions
GCC 8 moves a lot of unlikely code out of line to "cold" subfunctions in .text.unlikely. Properly detect the new subfunctions and treat them as extensions of the original functions. This fixes a bunch of warnings like: kernel/cgroup/cgroup.o: warning: objtool: parse_cgroup_root_flags()+0x33: sibling call from callable instruction with modified stack frame kernel/cgroup/cgroup.o: warning: objtool: cgroup_addrm_files()+0x290: sibling call from callable instruction with modified stack frame kernel/cgroup/cgroup.o: warning: objtool: cgroup_apply_control_enable()+0x25b: sibling call from callable instruction with modified stack frame kernel/cgroup/cgroup.o: warning: objtool: rebind_subsystems()+0x325: sibling call from callable instruction with modified stack frame Reported-and-tested-by: damian <damian.tometzki@icloud.com> Reported-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: David Laight <David.Laight@ACULAB.COM> Cc: Greg KH <gregkh@linuxfoundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/0965e7fcfc5f31a276f0c7f298ff770c19b68706.1525923412.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Josh Poimboeuf
Ingo Molnar
Родитель
0afd0d9e0e
Коммит
13810435b9
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@ -59,6 +59,31 @@ static struct instruction *next_insn_same_sec(struct objtool_file *file,
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return next;
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}
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static struct instruction *next_insn_same_func(struct objtool_file *file,
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struct instruction *insn)
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{
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struct instruction *next = list_next_entry(insn, list);
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struct symbol *func = insn->func;
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if (!func)
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return NULL;
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if (&next->list != &file->insn_list && next->func == func)
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return next;
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/* Check if we're already in the subfunction: */
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if (func == func->cfunc)
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return NULL;
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/* Move to the subfunction: */
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return find_insn(file, func->cfunc->sec, func->cfunc->offset);
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}
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#define func_for_each_insn_all(file, func, insn) \
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for (insn = find_insn(file, func->sec, func->offset); \
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insn; \
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insn = next_insn_same_func(file, insn))
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#define func_for_each_insn(file, func, insn) \
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for (insn = find_insn(file, func->sec, func->offset); \
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insn && &insn->list != &file->insn_list && \
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@ -149,10 +174,14 @@ static int __dead_end_function(struct objtool_file *file, struct symbol *func,
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if (!strcmp(func->name, global_noreturns[i]))
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return 1;
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if (!func->sec)
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if (!func->len)
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return 0;
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func_for_each_insn(file, func, insn) {
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insn = find_insn(file, func->sec, func->offset);
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if (!insn->func)
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return 0;
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func_for_each_insn_all(file, func, insn) {
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empty = false;
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if (insn->type == INSN_RETURN)
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@ -167,28 +196,17 @@ static int __dead_end_function(struct objtool_file *file, struct symbol *func,
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* case, the function's dead-end status depends on whether the target
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* of the sibling call returns.
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*/
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func_for_each_insn(file, func, insn) {
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if (insn->sec != func->sec ||
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insn->offset >= func->offset + func->len)
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break;
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func_for_each_insn_all(file, func, insn) {
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if (insn->type == INSN_JUMP_UNCONDITIONAL) {
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struct instruction *dest = insn->jump_dest;
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struct symbol *dest_func;
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if (!dest)
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/* sibling call to another file */
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return 0;
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if (dest->sec != func->sec ||
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dest->offset < func->offset ||
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dest->offset >= func->offset + func->len) {
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/* local sibling call */
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dest_func = find_symbol_by_offset(dest->sec,
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dest->offset);
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if (!dest_func)
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continue;
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if (dest->func && dest->func->pfunc != insn->func->pfunc) {
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/* local sibling call */
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if (recursion == 5) {
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/*
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* Infinite recursion: two functions
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@ -199,7 +217,7 @@ static int __dead_end_function(struct objtool_file *file, struct symbol *func,
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return 0;
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}
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return __dead_end_function(file, dest_func,
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return __dead_end_function(file, dest->func,
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recursion + 1);
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}
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}
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@ -426,7 +444,7 @@ static void add_ignores(struct objtool_file *file)
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if (!ignore_func(file, func))
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continue;
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func_for_each_insn(file, func, insn)
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func_for_each_insn_all(file, func, insn)
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insn->ignore = true;
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}
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}
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@ -786,9 +804,8 @@ out:
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return ret;
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}
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static int add_switch_table(struct objtool_file *file, struct symbol *func,
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struct instruction *insn, struct rela *table,
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struct rela *next_table)
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static int add_switch_table(struct objtool_file *file, struct instruction *insn,
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struct rela *table, struct rela *next_table)
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{
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struct rela *rela = table;
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struct instruction *alt_insn;
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@ -798,18 +815,13 @@ static int add_switch_table(struct objtool_file *file, struct symbol *func,
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if (rela == next_table)
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break;
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if (rela->sym->sec != insn->sec ||
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rela->addend <= func->offset ||
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rela->addend >= func->offset + func->len)
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alt_insn = find_insn(file, rela->sym->sec, rela->addend);
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if (!alt_insn)
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break;
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alt_insn = find_insn(file, insn->sec, rela->addend);
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if (!alt_insn) {
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WARN("%s: can't find instruction at %s+0x%x",
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file->rodata->rela->name, insn->sec->name,
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rela->addend);
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return -1;
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}
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/* Make sure the jmp dest is in the function or subfunction: */
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if (alt_insn->func->pfunc != insn->func->pfunc)
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break;
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alt = malloc(sizeof(*alt));
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if (!alt) {
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@ -947,7 +959,7 @@ static int add_func_switch_tables(struct objtool_file *file,
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struct rela *rela, *prev_rela = NULL;
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int ret;
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func_for_each_insn(file, func, insn) {
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func_for_each_insn_all(file, func, insn) {
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if (!last)
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last = insn;
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@ -978,8 +990,7 @@ static int add_func_switch_tables(struct objtool_file *file,
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* the beginning of another switch table in the same function.
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*/
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if (prev_jump) {
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ret = add_switch_table(file, func, prev_jump, prev_rela,
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rela);
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ret = add_switch_table(file, prev_jump, prev_rela, rela);
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if (ret)
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return ret;
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}
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@ -989,7 +1000,7 @@ static int add_func_switch_tables(struct objtool_file *file,
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}
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if (prev_jump) {
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ret = add_switch_table(file, func, prev_jump, prev_rela, NULL);
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ret = add_switch_table(file, prev_jump, prev_rela, NULL);
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if (ret)
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return ret;
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}
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@ -1753,15 +1764,13 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
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while (1) {
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next_insn = next_insn_same_sec(file, insn);
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if (file->c_file && func && insn->func && func != insn->func) {
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if (file->c_file && func && insn->func && func != insn->func->pfunc) {
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WARN("%s() falls through to next function %s()",
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func->name, insn->func->name);
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return 1;
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}
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if (insn->func)
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func = insn->func;
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func = insn->func ? insn->func->pfunc : NULL;
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if (func && insn->ignore) {
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WARN_FUNC("BUG: why am I validating an ignored function?",
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@ -1782,7 +1791,7 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
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i = insn;
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save_insn = NULL;
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func_for_each_insn_continue_reverse(file, func, i) {
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func_for_each_insn_continue_reverse(file, insn->func, i) {
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if (i->save) {
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save_insn = i;
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break;
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@ -1869,7 +1878,7 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
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case INSN_JUMP_UNCONDITIONAL:
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if (insn->jump_dest &&
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(!func || !insn->jump_dest->func ||
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func == insn->jump_dest->func)) {
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insn->jump_dest->func->pfunc == func)) {
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ret = validate_branch(file, insn->jump_dest,
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state);
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if (ret)
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@ -2064,7 +2073,7 @@ static int validate_functions(struct objtool_file *file)
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for_each_sec(file, sec) {
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list_for_each_entry(func, &sec->symbol_list, list) {
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if (func->type != STT_FUNC)
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if (func->type != STT_FUNC || func->pfunc != func)
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continue;
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insn = find_insn(file, sec, func->offset);
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@ -79,6 +79,19 @@ struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset)
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return NULL;
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}
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struct symbol *find_symbol_by_name(struct elf *elf, const char *name)
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{
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struct section *sec;
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struct symbol *sym;
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list_for_each_entry(sec, &elf->sections, list)
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list_for_each_entry(sym, &sec->symbol_list, list)
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if (!strcmp(sym->name, name))
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return sym;
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return NULL;
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}
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struct symbol *find_symbol_containing(struct section *sec, unsigned long offset)
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{
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struct symbol *sym;
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@ -203,10 +216,11 @@ static int read_sections(struct elf *elf)
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static int read_symbols(struct elf *elf)
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{
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struct section *symtab;
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struct symbol *sym;
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struct section *symtab, *sec;
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struct symbol *sym, *pfunc;
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struct list_head *entry, *tmp;
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int symbols_nr, i;
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char *coldstr;
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symtab = find_section_by_name(elf, ".symtab");
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if (!symtab) {
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@ -281,6 +295,30 @@ static int read_symbols(struct elf *elf)
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hash_add(sym->sec->symbol_hash, &sym->hash, sym->idx);
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}
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/* Create parent/child links for any cold subfunctions */
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list_for_each_entry(sec, &elf->sections, list) {
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list_for_each_entry(sym, &sec->symbol_list, list) {
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if (sym->type != STT_FUNC)
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continue;
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sym->pfunc = sym->cfunc = sym;
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coldstr = strstr(sym->name, ".cold.");
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if (coldstr) {
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coldstr[0] = '\0';
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pfunc = find_symbol_by_name(elf, sym->name);
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coldstr[0] = '.';
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if (!pfunc) {
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WARN("%s(): can't find parent function",
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sym->name);
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goto err;
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}
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sym->pfunc = pfunc;
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pfunc->cfunc = sym;
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}
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}
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}
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return 0;
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err:
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@ -61,6 +61,7 @@ struct symbol {
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unsigned char bind, type;
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unsigned long offset;
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unsigned int len;
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struct symbol *pfunc, *cfunc;
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};
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struct rela {
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@ -86,6 +87,7 @@ struct elf {
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struct elf *elf_open(const char *name, int flags);
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struct section *find_section_by_name(struct elf *elf, const char *name);
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struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset);
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struct symbol *find_symbol_by_name(struct elf *elf, const char *name);
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struct symbol *find_symbol_containing(struct section *sec, unsigned long offset);
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struct rela *find_rela_by_dest(struct section *sec, unsigned long offset);
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struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,
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